Abstract Submitted to the    NANOTUBE'04 Conference:

Single wall (SW) BN-NTs have been produced in important quantity and with a high degree of crystallinity by a vaporization laser technique [1]. The crystal structure and chemical composition of the collected soot have been characterized by very high resolution transmission electron microscopy (VHRTEM) and electron energy loss spectroscopy (EELS) [2]. EELS measurements in the valence band region have been performed in STEM (Scanning TEM) to obtain information on the electronic structure (band gap, plasmons analysis) of individual tubes. In contrast to C-NTs, BN-NTs are highly polar dielectric material, with a wide band gap close to 5.5 eV,largely independent of helicity and diameter. We thus perform resonant Raman measurements of the raw product [4] and of reference hexagonal BN by exciting with UV ligth in the 5.1-5.4 eV energy range. The experimental results are compared with ab-initio calculations performed by density-functional-theory in local density approximation [5].

[1] R. S. Lee, J. Gavillet, M. Lamy de la Chapelle, A. Loiseau, J.-L. Cochon, D. Pigache, J. Thibault, F. Willaime, PRB 64R, 121405 (2001)
[2] O. Stephan, A. Vlandas, R. Arenal de la Concha, S. Trasobares, A.Loiseau, C. Colliex, Proceedings EMAG (2003) and R. Arenal de la Concha, O. Stephan, A. Vlandas, A. Rubio, A. Loiseau (unpublished)
[3] R. Arenal de la Concha, O. Stephan, D. Taverna, M. Kociak, C. Colliex, A. Rubio, A. Loiseau (to be published)
[4] R. Arenal de la Concha, A. Ferrari, S. Reich, A. Rubio, A. Loiseau (unpublished)
[5] L. Wirtz, R. Arenal de la Concha, A. Rubio, A. Loiseau, PRB 68, 45425 (2003)